Upgrading the KSTAR YDC9101S UPS Battery

My KSTAR YDC9101S RT UPS battery died a couple of months ago. I’ve been delaying fixing it because I didn’t want a hackish solution since it involves electricity. I also didn’t want to put my servers offline for uncertain amount of time.

The manual says the my UPS battery is not user-serviceable, I was directed to call for a service. I didn’t want to.

I knew that it has to have a battery inside, I just need to figure out how to pull it out. I also didn’t know if I could take off the battery without the UPS shutting down.

How to remove the internal battery

A person uses a screwdriver to remove a screw from the front panel of a KSTAR UPS to access the internal battery.

Pull out the front panel
Remove the battery connector
Unscrew the 4 screws and the metal panel will be loose
Pull out the battery

A top-down view of the disassembled KSTAR YDC9101S UPS showing the internal battery compartment.

The battery is a lead-acid 12v9ah enclosed in a thick plastic. Connected in a series to make it 24v9ah.

Will the UPS work without battery?

Yes, as long as 1) Bypass mode is enabled in the settings 2) It has already started/working. Start up without battery does not work.

First attempt: Using original battery connector

The cost of 12v9ah battery is almost the same as 12v25ah. With 250%+ more capacity, I couldn’t justify buying the lower capacity.

The issue with 12v25ah is the form factor. It does not fit inside the UPS battery container.

What I end up doing is get the battery connector from the original battery and connect it to my new battery outside the unit.

A 12v25ah battery is connected to a KSTAR UPS using wires and a connector because it is too large to fit inside.

I wasn’t satisfied with this especially the battery connector is in front and I could not close the front panel.

Second attempt: Using External Battery Pack Connector

I read in the manual that this can support an external battery pack. It is also rack mounted and there’s a port at the back to connect it. This also gave me the confidence that it can support bigger capacity batteries.

I’m pretty sure that it’s just a parallel connection to the internal battery. What I did not know and not written in the manual is what type of port it’s using.